Biological Membranes & Transport Flashcards
Name 3 amphipathic lipid aggregates that form in water
micelle, vesicle, lipid bilayer
What is simple diffusion?
Nonpolar compounds move down concentration gradient
What is facilitated diffusion?
Molecule moves down its electrochemical gradient Requires transport channel Passive
What is primary active transport?
Molecule moves against its electrochemical gradient Requires transport channel ATP is used
What is secondary active transport?
Molecules moves against its electrochemical gradient Driven by an ion moving down its electrochemical gradient Requires transport channel Ion and molecule move in the same direction
What is an ion channel?
Molecule moves down its electrochemical gradient May be gated by a ligand or ion Requires transport channel
What is ionophore-mediated ion transport?
Molecule moves down its electrochemical gradient Ionophore picks up ion outside the cell, moves through membrane, drops ion off inside the cell, and can then repeat the cycle
Name the components of the phospholipid bilayer
Hydrophilic head (polar) and hydrophobic tail (nonpolar)
Why is cholesterol an important in the cell membrane?
Gives rigidity and intregrity to the membrate Has OH which allows it to be amphipathic It is a precursor of hormones
What causes archaea to have an unusual cell membrane?
Ether bond Causes lipid properties to withstand extreme temperatures
Permeability of phospholipid bilayer
From low permeability to high permeability: Ion (impermeable to phospholipid bilayer) Glucose, sucrose/ large uncharged polar molecules (impermeable) H2O, indole, glycerole/ small uncharged polar molecules (semipermeable) O2, CO2, N2/ hydrophobic molecules (freely permeable)
What is a peripheral protein?
A protein that is attached to the outside of the lipid bilayer.
What is an integral protein?
A protein that is free floating in the lipid bilayer Exposed ends are hydrophilic Strongest connection; must have detergent to remove from membrane Carboxy-terminis inside, amino-terminis outside
Explain the asymetric distribution of phospholipids in plasma membrane
Phospholipids that are high inside will be low outside, and vice versa
Explain the translipid deposition of glycophorin in an electrocyte
Carboxyl-terminis end inside Amino-terminis end outside
How do integral proteins embed into the phospholipid bilayer?
It has hydrophobic amino acids in its structure
How do lipid-linked membrane proteins attach to the phospholipid bilayer?
There is a protein component and a lipid component. Lipid component anchors the complex into the phospholipid bilayer by attaching to the hydrophobic tails
What is uniport?
Single molecule moves one direction across membrane Ex. glucose
What is symport?
Type of cotransport Two different molecules move in the same direction at the same time across the membrane Ex. glucose and Na
What is antiport?
Type of cotransport Two different molecules move in opposite directions at the same time across the membrane Ex. Na/K ATPase
Describe uncatalyzed transbilayer (“flip-flop”) diffusion
Lipid moves from one side of the lipid bilayer to the other (ex. inside border to the outside border) Occurs very slow
Describe uncatalyzed lateral diffusion
Lipid moves up or down the lipid bilayer on the same side Occurs very fast
Name the 3 enzymes involved in catalyzed transbilayer translocations
Flippase Floppase Scramblase
Name this membrane lipid and its class
Glycerophospholipid from the phospholipid class
Name this membrane lipid and its class
Sphingolipid from the phospholipid and glycolipid classes
Name this membrane lipid and its class
Cholesterol from the sterol class
What are lipid rafts?
specialized membrane microdomains that compartmentalize cellular processes
What are characteristics of caveolar membranes?
- they are membrane microdomains that have caveolin as the prinicpal component
- Caveolins may act as scaffolding proteins within caveolar membranes by compartmentalizing and concentrating signaling molecules
- receptor-independent endocytosis
How does simple diffusion without a transporter compare with diffusion with a transporter, in relation to entropy?
- simple diffusion without a tranporter will cause an increase in entropy
- diffusion without a transporter will cause a decrease in entropy
Describe the enzymatic action of carbonic anhydrase on carbon dioxide that occurs inside RBCs
- in respiring tissues, CO2 enters the RBC, where it is converted to carbonic acid and bicarbonate via carbonic anhydrase; bicarbonate is released into plasma
- in the lungs, bicarbonate and carbonic acid are converted to CO2 via carbonic anhydrase; CO2 is exhaled
